As a manufacturer of abrasive discs, let’s take a look at the production process of our cutting discs today; first, we start with raw materials. The surface of the raw sand is plated with iridium, which greatly improves the performance and quality and makes it more wear-resistant; then the molding Process, fully automatic production line, constant temperature and humidity in the workshop, beautiful sheet shape, in line with the needs of various markets; then high temperature baking, after 72 hours of temperature test, the perfect grinding wheel is released.
Specifically, first of all, the raw material of our grinding wheel is iridium-coated white corundum. Iridium-plated white corundum is a special abrasive made of corundum as raw material, after high temperature and high heat, a layer of metal iridium composite material is plated on the surface of the abrasive, and after calcination. After the corundum coated with iridium, the toughness of corundum is significantly improved, the surface is rougher, the hydrophilic ability is stronger, the self-sharpening property is increased, and the heat dissipation performance is improved. The abrasive products have the characteristics of working, long life and not easy to burn the workpiece.
Application range:
Iridium-plated abrasives are based on traditional abrasives, using new materials and technologies to improve white corundum abrasives. Compared with ordinary abrasives, the microhardness is increased by 10%, the toughness is increased by 10%, the hydrophilicity is increased by 350%, the grinding efficiency is increased by 30%, and the hardness is increased by 30-50%, which is very helpful for the improvement of the quality of grinding wheel products.
In addition, iridium-plated corundum can also be used in precision casting molding sand, spraying materials, raw materials for special ceramic products, refractory materials and other fields.
Most of the initial production are ceramic grinding wheels. The advantages of vitrified bonded grinding wheels are their natural porosity and good chemical stability, so they are suitable for dry and wet grinding, especially when using water-based and oil-based grinding fluids. However, the poor elasticity of ceramic grinding wheels and the need for high sintering temperatures limit its development. Phenolic resin bonded grinding wheel has the advantages of good elasticity and low sensitivity to shock, impact and lateral pressure. Its high stability enables it to adapt to higher rotational speeds and improves grinding performance, making it especially suitable for grinding and cutting wheels, and its good elasticity makes it suitable for ultra-precise grinding and surface polishing.
The production process of phenolic resin bond grinding wheel mainly includes cold pressing process, semi-hot pressing process and hot pressing process.
1. Cold pressing process:
The binders used in the cold pressing process include wetting agents and powdered resins. Usually, liquid phenolic resins, furfural, furfuryl alcohol, cresol, etc. are used as wetting agents. Liquid phenolic resins are the most used. The factors that determine the ratio of liquid resin to powder resin (usually called the liquid-to-powder ratio) are:
Abrasive particle size distribution, filler type, filler amount, viscosity of liquid resin, properties of powdered resin, etc. If the viscosity of the liquid resin is higher, more liquid resin is required to completely cover the surface of the abrasive; the smaller the particle size of the abrasive and filler, the larger the specific surface area and the higher the amount of liquid; the higher the molecular weight of the powdered resin The higher the high, the lower the free phenol, the poorer its adhesion to the liquid resin and the greater the amount of liquid required. All of the above situations need to increase the liquid-to-powder ratio. Generally, liquid resin is used as wetting agent, and the ratio of liquid to powder is 1:2-1:4, while the mixture of furfural or furfuryl alcohol and anthracene oil is used as wetting agent, and the ratio of liquid to powder is 1:6-1:8.
The mixer should be verified by the process, and it is better to achieve the ideal mixing effect and not damage the abrasive. The mixing time after adding the fine powder is generally 2-5 minutes. If it is too short, it cannot ensure uniform mixing. If the resin film is too long, it will easily fall off, and the temperature of the material will rise and the resin will be pre-cured.
The mixing procedure is as follows:
First, premix the abrasive, usually with a mixed particle size, and then add a wetting agent to evenly wet the abrasive, then add the powdered resin that has been premixed with other powdery fillers, and continue to mix until uniform. The mixed abrasive should have good plasticity and fluidity. The material should not be too wet, otherwise it will be easy to agglomerate, and there should be no lumps. At the same time, it must have good fluidity to ensure sufficient injection molding. Generally, the method of sieving is adopted. Remove lumps.
The method of judging the plasticity of materials is as follows:
Grab a handful of the mixed ingredients, and gently knead them with your hands to form a ball. Generally, adding powdery materials to the wetted abrasive is easy to form a powder mass, which has been gradually eliminated at present. Now, the two-pot mixing method is more commonly used, that is, the abrasive and the wetting agent are first mixed in a mixing machine. Mixing, at the same time, mix the powdery resin and other powdery fillers in another mixer, and then pour the wetted abrasive into the powder and mix evenly. The advantage of double pot mixing is that it can not only produce no lumps, but also avoid pollution, and it is easy to clean the pot. After sieving the mixed material, it can be used for pressing.
The compression procedure is as follows:
Install the mold, weigh the required amount of abrasive and add it into the mold cavity, scrape it flat and press it. Those who need to place the reinforced glass fiber mesh are placed as required. Then pressurize at room temperature. Generally, the pressure range of cold pressing is 15-30 N/mm2, preferably 15-25 N/mm2. The choice of pressure depends on the plasticity of the material and the required density of the grinding wheel. Excessive pressure should not be used, otherwise the abrasive will be crushed. The pressing time is generally 5-50 seconds, preferably 5-30 seconds. The length of time depends on the required density and shape of the grinding wheel and the plasticity of the material. The grinding wheel can then be taken out for the next step – curing.
The curing procedure is as follows:
The curing operation can be carried out in a fixed curing furnace or in a flowing tunnel curing kiln. It is cured in a curing furnace. The placement position of the grinding wheel is particularly important. Generally, the grinding wheel is fixed with a steel or ceramic disc to ensure that the grinding wheel does not deform during the curing process, and is evenly placed in the furnace. All parts are heated evenly, and then start the heating program for curing; use a tunnel-type curing kiln to cure, first fix the grinding wheel with a steel or ceramic disc, then place it in the trolley, push it into the tunnel, and run at the set speed. Generally, the initial temperature is 60-80 ℃, and the final temperature is 160-190 ℃. The whole curing process takes 20-25 hours, and finally the temperature is lowered to 40-60 ℃, and the furnace door can be opened to take out the grinding wheel.
Physical and chemical changes occur during the entire heating process, and the following reactions occur at each temperature stage: At 80 °C, the resin begins to melt, water evaporates, and the curing reaction begins; at 110 °C, it decomposes six times and promotes cross-linking of the molten resin. At the same time, ammonia, water and other gases are released; 110-180 ℃ resin is cross-linked until it is completely cured, and a large amount of ammonia is released. Excessive time in the high temperature zone will lead to over-curing of the resin. When the hardness of the grinding wheel increases, the strength of the grinding wheel decreases. Generally, different curing curves and final curing temperatures are selected according to the different requirements of the grinding wheel. When the final temperature is 165-170 °C, the grinding wheel is hard and tough; when the final temperature is 175-180 °C, the grinding wheel is hard; when the final temperature is 185-190 °C, the grinding wheel is hard and brittle
2. Semi-hot pressing process:
The pressing temperature of the semi-hot pressing process is generally 50-65 °C, and the rest of the processes are completely consistent with the cold pressing process. At this pressing temperature, the viscosity of the liquid resin becomes smaller, and the powdery resin can be well integrated, so that the fluidity of the entire resin system is improved, and it is easier to fully penetrate each space, even if the pressure of the press is not too high. , it can also be well formed, and the pressure holding time does not need to be too long, especially suitable for continuous automatic pressing production lines.
3. Hot pressing process:
The hot pressing process is generally used to manufacture grinding wheels with larger density. The density of ordinary grinding wheels is generally 2.4-2.7g/cm3, and the highest is 2.9g/cm3, while the density of high-density grinding wheels can reach 3.1-3.5g/cm3. To achieve this For high density, hot pressing process is the most suitable. The mixing requirements of the hot pressing process are different from those of the cold pressing process. Generally, the dry mixing method is used, or the abrasive is wetted with furfural less than 1% of the weight of the abrasive as a wetting agent, and then mixed with the powder resin evenly. The powdery resin is generally selected with low fluidity, and the suitable range is 15-20mm or even smaller. Liquid resin and powdery resin with high fluidity cannot be used because it is easy to leak grease during hot pressing.
suppress:
The pressing temperature range is 160-170℃, and the pressing time is 30-60 seconds/mm thickness of the grinding wheel. For example, for pressing a 60mm thick grinding wheel, please refer to the following requirements: Pressure: 20-40N/mm2; Pressing temperature: 150-170℃; Pressing time : 30-60 minutes. During the pressing process, the air should be deflated once or several times within 4-8 minutes after the pre-pressing. Curing: The hot-pressed grinding wheel already has considerable strength, but it still needs to be cured to achieve the best performance. The curing temperature is 160-180 ℃, and the curing time is 8-12 hours.
